This invention relates to an anti-theft device for motor vehicles, and more particularly to a small unnoticeable device that renders the motor inoperable until the operator satisfies a pre-determined set of conditions.
The problem of automobile thefts is well recognized and constitutes a significant problem. Many of the automobiles are never recovered. Others are recovered in damaged or stripped condition.
More recently, the hijacking or theft of loaded trucks has been a problem of increasing seriousness. While these vehicles are usually recovered, the valuable cargoes are usually not.
A wide variety of devices have been suggested to deter such thefts. For example, U.S. Pat. Nos. 3,930,226 and 3,858,175 show devices which sound the horn of the vehicle when someone tampers with the door, hood, gas tank or auxiliary switch. However, this device is disabled when the ignition switch is turned on and would be totally ineffective against a thief who had access to keys or who could "pick" the ignition switch lock. Moreover, the horn could obviously be silenced simply by disconnecting or cutting the wire.
Other devices with hidden switches or locks for deactivating an alarm or "protection" system have been suggested, as for example by U.S. Pat. Nos. 4,107,543 and 3,750,430.
Numerous combination or sequence type devices have also been suggested; e.g. by U.S. Pat. Nos. 3,544,804; 3,691,396; 3,818,436; and 4,064,547. However, each of these devices includes a keyboard or one or more dials which immediately give away the presence of the device. The experienced thief can then quickly re-route or bypass the protective mechanism.